1. Field of the Invention
The invention relates to a mould for the manufacture of a casting using moulding material and a method for the manufacture of such a mould.
2. Description of Related Art
Castings which frequently have a complex shape are usually manufactured in so-called “dead” moulds or in permanent moulds. During casting in dead moulds which generally consist of a mineral, refractory, granular basic material, such as quartz sand or chrome ore sand as well as a binder and frequently also other additives to improve the properties of the moulding material, the mould is destroyed by the unpacking process after the casting. In connection with casting in dead moulds, a model of the casting is first made of metal, wood, gypsum or plastic. The model forms the outer contour of the base piece. The model is basically re-usable. In order to produce the mould, the upper and lower part of the model is positioned in a mould box, i.e. an upper box and a lower box, and surrounded by the moulding material. After compacting and hardening the moulding material, the model parts are withdrawn from the sand mould. The upper and lower boxes are then placed one above the other. The negative mould is thus completed.
Casting using dead moulds is used especially for Fe-based high-melting alloys. A disadvantage with casting using dead moulds is that after each casting process not only a new mould must be produced but the re-processing or removal of the moulding material after casting is associated with a high installation and financial expenditure. It is especially important in this connection that the mould boxes for the manufacture of the moulds usually have a standard shape so that a relatively large quantity of moulding material is required for small castings in order to be able to produce the mould.
A further disadvantage during casting using dead moulds is that cooling segments cannot be positioned exactly. Cooling segments are usually used in a dead mould to create a temperature gradient and to set a guided solidification. Beginning from the “end zone” of a casting, the feed flux to the “feeder zone” is hereby facilitated. Cooling segments are placed loosely on the model in the respective box and fixed by the moulding material which surrounds them. During the compaction of the moulding material the exact position of the cooling segment can be lost. However, the exact positioning of cooling segments is of considerable importance in the casting of thin-walled castings.
During casting in permanent moulds hundreds to hundreds of thousands of castings can be achieved using the same moulding device. Permanent moulds have become exceptionally important for the comparatively low-melting non-ferrous metal cast work-pieces since the thermal stressing which imposes limits on the permanent moulds is acceptable because of the relatively low casting temperatures for non-ferrous metals. Cast iron work-pieces and steel can fundamentally also be cast in permanent moulds but the associated costs for the production and maintenance caused by the moulding materials used (e.g. graphite, sintered metals, ceramic materials) are very high. Permanent moulds suitable for the casting of cast iron work-pieces and steel are thus very expensive and very liable to wear as a result of the high thermal loading of the cracks forming in some parts or as a result of the local melting of the mould.